1. Field of the invention
The present invention relates generally to a fusible link. More particularly, the present invention relates to a cartridge type fusible link wherein a fuse element composed of a female terminal member is received in a housing of the fusible link.
2. Prior art
For example, as shown in FIG. 5, a conventional cartridge type fusible link is constructed such that an opposing pair of female terminal members 10 each including an electrical contact portion 11 at one end as seen in the longitudinal direction thereof are arranged in a housing 30 and a fuse element 20 including a fusible portion 12 between the other ends of the female terminal members 10 is received in the housing 30 (e.g. Unexamined Japanese Utility Model Application Sho. 64-33146).
With the conventional fusible link constructed in the above-described manner, the housing 30 includes receiving chambers 32 in each of which stepped engagement portion 32a is formed to receive a lance 11a extending upwardly from the electrical contact portion 11 as illustrated within the range defined by a circle P in the drawing. Thus, undesirable disconnection of the fuse element 20 from the housing 32 can reliably be prevented by bringing the lance 11a in engagement with the stepped engagement portion 32a.
A cover member (hereinafter referred to simply as a cover) 40 adapted to cover an opening portion 30a of the housing 30 therewith is fitted to the housing 30 while the fuse element 20 is received in the housing 30, whereby invasion of dust or similar foreign materials from the outside is prevented by the cover 40 so as to protect the fuse element 20 from the invasion of the dust or the like, and moreover, scattering of small fused pieces away from the housing 30 to the outside at the time of fusion of the fuse element 20 is prevented by the cover 40.
In addition, a proposal has been made as to other type of method of holding a fuse element in a housing in the engaged state wherein disconnection of the fuse element from the housing is prevented by bringing each housing lance formed in the housing in engagement with the corresponding engagement hole formed in an electrical contact portion of the fuse element.
Each of the conventional fusible links constructed in that way is employed for a circuit through which a comparatively high intensity of electric current is required to flow. Since connected locations on the fuse element have small contact resistance, the fuse element is reliably secured to the housing, and the fuse element can easily be replaced with a new one after an occurrence of fusion, many conventional fusible links of the foregoing type are put in practical use.
With respect to the conventional fusible links constructed in the above-described manner, however, since the engagement of the fuse element with the housing is achieved merely by primary engagement of the lances with the stepped engagement portions, there arises a malfunction that both male and female terminals come in incorrect contact with each other due to unsatisfactory connection therebetween. Specifically, in case of a fusible link of the type wherein male and female terminals are connected to each other by inserting the male terminal from the outside into the opponent female terminal received in the housing, since the male terminal is squeezed against the clamp force of the female terminal at the time of fitting of the male terminal into the opponent female terminal, there arises an occasion that if the fuse element is insufficiently retained in the housing, as the male terminal is squeezed in the housing, the fuse element may be dislocated by the action of the clamping force of the female terminal in the rearward direction, resulting in the male terminal failing to be firmly engaged with the female terminal.
In view of the forgoing problem, an object of the present invention is to provide a fusible link which assures that incorrect insertion of a fuse element can reliably be prevented, and moreover, the fuse element can immovably be held in the double engaged state without any possibility that both male and female terminals are incompletely connected to each other.
To accomplish the above object, the present invention provides a fusible link including a housing molded of an electrical insulative material and having an opening portion formed thereon, a fuse element adapted to be inserted into the housing through the opening portion so as to be firmly engaged with the housing, and a cover member fitted to the housing while covering the opening portion of the housing therewith, wherein a plurality of projections for preventing the fuse element from being incorrectly inserted into the housing by bringing the foremost ends of the projections in contact with the fuse element are projected from the inner surface of the cover member.
When the projections extending from the inner surface of the cover member are inserted into the housing while the foremost ends of the projections are brought in contact with the fuse element, lances slantwise extending from the fuse element are engaged with stepped engagement portions on the housing so as enable the fuse element to be firmly held in the housing. Since the foremost ends of the projections come in contact with the fuse element when the cover member is fitted to the housing, the fuse element can reliably be held in the housing at a predetermined position without any possibility of dislocation of the fuse element from the predetermined position. Consequently, the fuse element is immovably held in the housing in the double engaged state by the engagement of the lances with the stepped engagement portions on the housing as well as the engagement derived from the continuous contact of the foremost ends of the projections with the fuse element attained by the fitting of the cover member to the housing.